Combinatorial weighing method and apparatus

Abstract

A combinatorial weighing method and apparatus wherein a value serving as a target for a combinatorial computation is set so that the mean weight value of batches of articles weighed out selectively by plural weighing cycles becomes equal to a preset weight value within preset allowable limits. Combinatorial computations are performed while diminishing the target weight value by a predetermined amount when the mean weight value is greater than the preset weight value, and increasing the target weight value by a predetermined amount when the mean weight value is less than the preset weight value.

What we claim is: 
     
       1. A combinatorial weighing method carried out under the control of a control unit for performing combinatorial computations based on weight values produced as outputs by respective ones of a plurality of weighing machines which measure the weights of articles supplied thereto, the control unit selecting a combination of weighing machines whose articles have a total combined weight value within preset allowable limits, and discharging the articles from the weighing machines belonging to the selected combination, said method comprising the steps of: (a) calculating a mean wieght value for the total combined weight values selected during a plurality of weighing cycles;   (b) setting a target weight value, which serves as the target for the combinatorial computations performed by the control unit, so that the mean weight value approaches a preset weight value which is within the preset allowable limits; and   (c) performing combinatorial computation while diminishing the target weight value by a predetermined amount when the mean weight value is greater than the preset weight value, and increasing the target weight value by a predetermined amount when the mean weight value is less the preset weight value.   
     
     
       2. The method according to claim 1, further comprising the step of setting the initial value of the target weight value to be equal to the preset weight value. 
     
     
       3. The method according to claim 2, further comprising the step of selecting a combination of weighing machines whose articles have a total combined weight value closest to the target weight value within the preset allowable limits when the mean weight value is greater than the preset weight value. 
     
     
       4. The method according to claim 2, further comprising the step of selecting a combination of weighing machines whose articles have a total combined weight value closest to but not less than the target weight value when the mean value is less than the preset weight value. 
     
     
       5. The method according to claim 2, wherein said step (a) comprises calculating the mean weight value whenever articles are discharged a predetermined number of times. 
     
     
       6. The method according to claim 5, wherein said step (a) further comprises: calculating the mean weight value by dividing a sum of the total combined weight values of discharged articles by a discharge number corresponding to the number of times articles are discharged; and   clearing the sum and the discharge number to zero at predetermined intervals.   
     
     
       7. The method according to claim 1, further comprising the step of selecting a combination of weighing machines whose articles have a total combined weight value closest to the target weight value within the preset allowable limits when the means weight value is greater than the preset weight value. 
     
     
       8. The method according to claim 1, further comprising the step of a selecting a combination of weighing machines whose articles have a total combined weight value closest to but not less than the target weight value when the mean weight value is less than the preset weight value. 
     
     
       9. The method according to claim 1, wherein said step (a) comprises calculating the mean weight value whenever articles are discharged a predetermined number of times. 
     
     
       10. The method according to claim 9, wherein said step (a) further comprises: calculating the mean weight value by dividing a sum of the total combined weight values of discharged articles by a discharge number corresponding to the nurber of times articles are discharged; and   clearing the sum and the discharge number to zero at predetermined intervals.   
     
     
       11. A combinatorial weighing apparatus having a plurality of weighing machines for measuring the weights of articles supplied thereto and for outputting respective weight values used for performing combinatorial computations to select a combination of weighing machines whose articles have a total combined weight value within preset allowable limits, and to discharge the articles from the weighing machines belonging to the selected combination, said apparatus comprising: means for calculating a mean weight value for the total combined weight values selected during a plurality of weighing cycles;   means for setting a target weight value, which serves as the target for the combinatorial computations, so that the mean weight value approaches a preset weight value which is within the preset limits; and   means for performing combinatorial computation while diminishing the target weight value by a predetermined amount when the mean weight value is greater than the preset weight value, and incresing the target weight value by a predetermined amount when the mean wieght value is less than the preset weight value.   
     
     
       12. The apparatus according to claim 11, further comprising means for selecting a combination of the weighing machines whose articles have a total combined weight value closest to the target weight value within the preset allowable limits when the mean weight value is greater than the preset weight value. 
     
     
       13. The apparatus according to claim 11, further comprising means for selecting a combination of the weighing machines whose articles have a total combined weight value closest to but not less than the target weight value when the means weight value is less than the preset weight value. 
     
     
       14. The apparatus according to claim 11, wherein said calculating means comprises means for calculating the mean weight value whenever articles are discharged a predetermined number of times. 
     
     
       15. The apparatus according to claim 14, wherein said calculating means further comprises: means for obtaining the mean weight value by dividing a sum of the total combined weight values of discharged articles by a discharge number corresponding to the number of times articles are discharged; and   means for clearing the sum and the discharge number to zero at predetermined intervals.   
     
     
       16. A combinatorial measuring method comprising the steps of: (a) determining, during a weighing cycle, the weights of a plurality of batches of articles, and providing weight values corresponding to the respective weights of the batches of articles;   (b) performing, during a weighing cycle, combinatorial computation based on the weight values provided in said step (a) to select the combination of batches having a total combined weight value which is closest to a target weight value within preset allowable limits;   (c) selectively calculating a means weight value for the total combined weight values corresponding to the combinations selected in said step (b) during a plurality of weighing cycles;   (d) adjusting the target weight value so that the mean weight value approaches a preset weight value which is within the preset allowable limits, said adjusting step comprising the substeps of: (i) diminishing the target weight value by a predetermined amount when the mean weight value is greater than the preset weight value; and   (ii) increasing the target weight value by the predetermined amount when the mean weight value is less than the preset weight value.     
     
     
       17. The method according to claim 16, wherein said step (b) comprises the step of selecting the combination of batches of articles having a total combined weight value closest to but not less than the target weight value when the mean weight value is less than the preset weight value. 
     
     
       18. The method according to claim 16, wherein said step (b) comprises selecting the combination of batches of articles having a total combined weight value closest to the target weight value within the preset allowable limits when the sean weight value is greater than the preset weight value. 
     
     
       19. The method according to claim 16, wherein said step (c) comprises calculating the mean weight value after a predetermined number of weighing cycles have occurred. 
     
     
       20. The method according to claim 19, wherein said step (c) further comprises: calculating the mean weight value by dividing a sum of the total combined weight values of discharged articles by a discharge number corresponding to the number of weighing cycles; and   clearing the sum and the discharge number to zero at predetermined intervals.